Apparatus for igniting and operating gaseous discharge devices



A g. 3, 1954 A. E. FEINBERG ET AL 2,685,662

APPARATUS FOR IGNITING AND OPERATING GASEOUS DISCHARGE DEVICES Filed May5, 1950 3 Sheets-Sheet l mm mm) QM 52 ll" ill! 2 y f/meg Aug. 3, 1954 A.E. FEINBERG ETAL 2,635,662

APPARATUS FOR IGNITING AND OPERATING GASEOUS DISCHARGE DEVICES Filed May5, 1950 3 Sheets-Shet 2 Aug. 3, 1954 A. E. FEINBERG ET AL 2,635,662

APPARATUS FOR IGNITING AND OPERATING GASEOUS DISCHARGE DEVICES Filed May5, 1950 3 Sheets-Sheet 3 Patented Aug. 3, 1954 APPARATUS FOR IGNITINGAND OPERAT- ING GASEOUS DISCHARGE DEVICES Albert E. Feinberg and PaulBerger, Chicago, 111., assignors to Advance Transformer 00.. Chicago,111., a corporation of Illinois Application May 5, 1950, Serial No.160,366

Claims. 1

This invention relates generally to apparatus for providing the ignitionand Operation voltage for a plurality of gaseous discharge devices, andmore particularly is concerned with apparatus intended for igniting andoperating fluorescent lamps connected in groups, and especially groupsof four.

The type of apparatus which is contemplated by our invention is commonlyknown as a bal last, and one of the basic components of such apparatusis a transformer. The invention herein includes a transformer in whichthe windings are arranged in a novel manner to give certain beneficialresults.

It is obvious that many types of ballasts exist which are intended forthe ignition and operation of single lamps and pairs of lamps. It hasbeen customary that the circuits include some manner of switch, so thatthe filaments of the lamps are heated to cause emission of clouds ofelectrons, and the application of suitable ignition voltage across anygiven lamp simultaneously with the heating of the filaments eventuallywill cause a breakdown of the gases in the lamp. Thereafter the lampwill pass current freely, at relatively low voltage, the current beinglimited by the impedance of the connected windings of the startingtransformer. As an example, a so-called hot cathode lamp presently knownas the T-12 and having a rating of watts ignites at a voltage ofapproximately 200, and operates at approximately 110 volts.

The relatively long lapse of time between applying the line voltage tothe apparatus and ignition of the lamps led to the development of theso-called instant-start type of lamp, in which the lamp is ignitedalmost the instant that the power is applied to the ballast. In sucharrangements, obviously there is no need for preheating anelectron-emitting filament. Instead a relatively high voltage is appliedacross the terminals of a lamp constructed to withstand the resultingstresses, and ignition occurs, with the usual decrease in voltage acrossthe lamp as the current flows. Thus, a lamp known as the T-12, 96 inch'75 watt hot cathode fluorescent lamp will ignite at approximately 625volts and operate at approximately 195 volts.

In practically all cases, the power line avail-- able for the operationof the lamps consists of 110 to 118 volts A. C. at or cycles per swond.Obviously it is necessary to transform the voltage to a considerablyhigher value in order to ignite and operate instant-start lamps.Apparatus for instant-start fluorescent lamps is shown and described inco-pending applications of Albert E. Feinberg, Serial No. 97,381, filedJune 6, 1949, now Patent No. 2,599,188 issued May 23, 1950, and SerialNo. 135,669, filed December 29, 1949, now Patent No. 2,558,293, issuedJune 26, 1951, said first application being entitled Transformer andsaid second applicaion being entitled Apparatus for tarting andOperating Gaseous Discharge Devices. As pointed out in the second ofsaid applications, one manner of igniting the instant-start type offluorescent lamps is to apply the starting voltage across the lampsseriatim whereby after one has started, ignition voltage is available tothe second lamp.

The seriatim or series starting method is desirable because of the highvoltages which must otherwise be used. Obviously if a voltage of 600 to700 volts is required to start one lamp, two lamps connected in serieswill require twice that voltage. If the lamps are operated in parallel,equal voltages of the same value, namely, capable of causing ignitionmust simultaneously be developed across each lamp. The size and cost ofthe required transformers are considerable. It is not desirable to usehigh voltages for series connected simultaneously starting lamps inapparatus which is operated from a low voltage line, and which isassociated with ordinary lighting fixtures. The problem of providing thenecessary voltages is therefore increased many fold when it is desiredto operate three or four lamps at one time, in one fixture.

The principal object of this invention is to provide novel apparatus forigniting and thereafter operating three or four gaseous dischargedevices from a single transformer.

Heretofore, in th eevent that more than a pair of instant-start lampswere intended to be used, it was required that the starting apparatusfor the pair be duplicated resulting in large, heavy, and expensiveballasts. By the use of certain ingenious arrangements we have been ableto provide apparatus using a single transformer for the efficientignition and operation of four instant-start lamps which is economicaland simple in construtcion, which is eflicient in operation, relativelysmall in size, and light in weight.

It has been desirable in operating pairs of fluorescent lamps fromcommercial volt lines to utilize the so-called lead-lag circuits inwhich one lamp is operated with a leading power fac tor and the otherwith a lagging power factor so as not to upset the line power factor toogreatly and also to eliminate to a great extent the stroboscopic effectof such lamps. The conventional manner of doing this has been to inserta condenser in the reactive circuit of one of the lamps. Our inventionhas also been devised with this in mind, namely to provide leading andlagging circuits to result as closely as possible in unity power factorin the line.

The safety requirements set up by certain standards committees andorganizations for apparatus of the type contemplated herein are somewhatrigid, but by reason of our invention readily can be complied with inthe cons ruction of a ballast in accordance with the teaching thereof.One important requirement of practically all codes is that at no pointin the entire circuit or apparatus shall there by any voltage whichrequires excessive insulation or unusually heavy lead wire. Obviouslythis requirement is to eliminate hazards to life, and possibleflashovers. A second requirement is that the circuit of the apparatusmust be arranged so that the removal or any lamp must completelydeenergize the ballast. The sockets for instantstart lampsconventionally used at present consist essentially of two-contactdevices normally open but bridged by the single terminal of the lamp.The sockets are connected in series with the line so that the removal ofthe lamp will open the line. This requirement means that each lamp of agroup operated by a single ballast must have at least one end thereofarranged to be connected to the line.

Accordingly, it is another object of our invention to provide apparatusof the character described for operating a plurality of gaseousdischarge devices in which each of the devices adapted to be operatedthereby will be enabled to have one terminal contacting the linedirectly.

In the event that the second requirement above referred to need not becomplied with, certain modifications of our invention enable theconstruction of a more economical ballast, as will be explainedhereinafter, and certain other objects of the invention are concernedwith the provision of this type of apparatus.

Considering the last mentioned type of apparatus, namely, in whichcertain of the fluorescent lamps connected therewith may not have atleast one terminal thereof connected directly to the line, it should beobvious that the same could be used in fulfilment of the said secondrequirement in connection with sockets which have line switchesassociated therewith and arranged to operate when the lamp is inserted,but without establishing contact between the lamp terminal and the line.Such sockets are not of the present conventional type, but thefeasibility thereof should be obvious to those skilled in the art whenhereinafter pointed out.

Another important object of the invention is to provide apparatus forigniting and thereafter enabling the operation of four instant-startfluorescent lamps or similar gaseous discharge devices having negativeresistance characteristics, which apparatus utilizes two series startingcircuits arranged in parallel with each series starting circuit havingtwo lamps therein.

Still a further object of the invention is to provide, in apparatus ofthe character described which includes leading and lagging seriesstarting circuits, auxiliary starting means for each circuit having areactive character opposite to that of the circuit.

Many other objects should occur to those skilled in the art to whichthis invention pertains, and

many advantages will become apparent as the description proceeds. Inconnection with the description we have, for explanatory purposes,illustrated preferred embodiments of our invention, showing the mannerof construction, assembly and use thereof, but it should be apparentthat many variations are possible in the electrical circuits, value ofthe circuit elements, and size and shape of the parts of the illustrateddevice without departing from the spirit of the invention as set forthin the appended claims.

In the figures:

Fig. i is a top plan view of a transformer constructed in accordancewith our invention in order to show the arrangement of the windings uponthe core.

Fig. 2 is a schematic circuit diagram showing the conn ctions of thetransformer of Fig. 1 in a circuit embodying our invention, same beingconnected with four fluorescent lamps for igniting and operating thesame.

Fig. 3 is a schematic circuit diagram identical to that of Fig. 2 butrearranged for clarity in explanation.

Fig. 4 is a view similar to that of Fig. 1, but on a reduced scale,showing a modified form thereof.

Figs. 5 and 6 are vector diagrams of certain phenomena explained in thespecification.

Fig. 7 is a schematic circuit diagram of a modified form or" theinvention.

Fig. 8 is a top plan view of a transformer constructed in accordancewith the principles de scribed in connection with Fig. '7.

Fig. 9 is a sectional view through a socket suitable for use inconnection with the apparatus of Fig. '7.

Referring now to Figs. 1 to 3 inclusive we have shown a preferredembodiment of our invention incorporated into apparatus for starting andoperating four fluorescent lamps. The reference character {it designatesgenerally the transformer upon which the inductive windings are arrangedas will hereinafter be explained. The transformer 26 includes a stack oflaminations forming an elongate rectangular shell 2!, having a pluralityof windows (not visible in the drawings) formed therein. The windingsare disposed in said windows, and we prefer arranging the windings upona central elongate winding leg 22 which matingly seats in the shell 2!as indicated by the end joints 2-3 and 2A. In production, the windingsmay be pre-assembled to the winding leg 22 which is then pressed homeinto the shell 2!.

Considering the windings, in the embodiment shown in Figs. 1 to 3inclusive there are five windi gs, all commonly mounted upon the leg 22.rting with the left end of Fig. 1 these windings re as follows: Firstthere is provided the winding 25 which is separated from the nextwinding by the magnetic shunt lit and which shall be termed theauxiliary starting secondary winding; this is followed by the firstprimary winding 2?, the leading secondary winding 28; thereafter wedispose the lagging seondary winding 29 separated from the leadingsecondary winding by othe magnetic shunt 35 and finally the second ismounted on the extreme right hand end of the winding leg 22 separatedthe lagging secondary winding by a third magnetic shunt 32 somewhatlarger than either of the other two.

The magnetic shunts 25, 3B, and 32 are provided with non-magnetic gaps33, 34 and 35 which provide the high magnetic reluctance to cause thedesired de-coupling between the adjoining winde ings whereby highleakage flux results and high reactances are achieved in the desiredwindings.

In Fig. 2 we have shown the circuit diagram of the apparatus with thewindings of the transformer 2|] oriented in the exact sequence describedin connection with Fig. 1, and the core 2 |-22 is conventionallydesignated by the parallellines extending throughout the length of allof the windings. Likewise, the conventional designation for the magneticshunts 26, 30 and 32 is used between the appropriate windings. While allconnections properly have been made in Fig. 2, the parts have beenre-oriented in Fig. 3 in order better to explain the operation thereof.

Four fluorescent lamps, designated 4|, 42, 43 and 44 are connected inelectrical association with the windings of the transformer Ell in amanner to be explained. As best shown in Fig. 2, the left hand terminalsof the lamps 4| and 42 connect directly to one side 45 of a power line,say 60 cycle A. C. 110-118 volts, while the left hand terminals of thelamps 43 and 44 connect directly to the second side 46 of the same line.Since one terminal of each lamp connects directly with the line, it is asimple manner to arrange the connections so that the removal of any lampwill open the line on either side. The socket connections are shownschematically at 40, 41, 48 and 49 in Fig. 2 and the operation thereofis believed obvious. The exact construction of the sockets forms no partof this invention, although it should be appreciated that by reason ofthe invention, such sockets are capable of being used with all fourlamps to open the line in the event of removal of any one lamp. For thisexplanation and example, the lamps will be considered as T-l2instant-start fluorescent lamps, having a rating of '75 watts each, 96inches in length, with an ignition voltage of 625, an operating voltageof 195 at which a current of 425 milliamperes is drawn.

Referring now to Fig. 3, the two line terminals 45 and 46 connect tojunctures 5| and 52 respectively. The first primary winding 21, the leftend of the lamp 4|, and the left end of the lamp 42 are all connected tothe juncture 5|. The second primary winding 3! is connected in serieswith the first primary winding 21 by the lead 53. The right hand end ofthe second primary winding 3| (as viewed in Fig. 3) is connected withthe juncture 52 so that the entire primary is across the line terminals45 and 46 and obtains therefrom the total line voltage. It is desired topoint out at this time, however, that the primary is split, part beingdisposed on one end of the transformer and part on the opposite end forpurposes to be explained hereinafter. This is best understood by thearrangement of Fig. 2. Although we have termed the winding 21 the firstprimary winding and the winding 3| the second primary winding, thedesignation is purely arbitrary since the relative size is not intendedto be limited thereby. The primary may be split substantially in half,or may be divided in portions having other than an equal division of theturns, depending upon other design factors capable of wide variation.

The auxiliary starting secondary winding 25 has its left hand end (asviewed in Fig. 3) connected to junction 52, while its right hand end isconnected to the left hand end of the leading secondary winding 28 andthe condenser 55, the juncture being designated 56. Said condenser 55 isconnected to the right hand end of the lamp 4|. The right hand end ofthe leading secondary winding 28 (as viewed in Fig. 3) connects to lamp44. The lagging secondary winding 29 is connected on its left hand end(as viewed in Fig. 3) to the lamp 42, and on its right hand end to thelamp 43 whose left hand end together with that of lamp 44 is connectedto juncture 52. Lamp 43 is shunted by a resistance-capacitance branchconsisting of a register 5'! and a capacitor 58.

The normal direction of instantaneou voltage in each of the windings isindicated by a solid line arrow shown parallel to the respective windingand designated by the same characters used to designate the windings,except that the characters are primed. In connection with the explanation of the operation of the device, note that the arrows 2?, 3|and 25' are all directed to the right indicating that the voltagesthereof are arranged to reinforce one another, while the arrows 28 and23 are directed to the left indicating that the voltage from thesewindings reinforce one another, but in opposition to the voltagerepresented by the other three windings. Under certain conditions, thevoltage in the auxiliary starting secondary windings acquires aquadrature component of such phase that the net resultant causes areversal of voltage, giving rise to the effect indicated by the brokenline arrow 25" pointing in direction opposite to arrow 25'.

The circuit described consists essentially of two pairs of seriesconnected and operated lamps arranged in parallel. The series lamps are4| and 44 connected in parallel with the series lamps 42 and 43. Closingthe circuit to the terminals 45 and 48 will resuit in ignition of allthe lamps almost immediately thereafter, followed by proper regulationof the lighted lamps. The manner of operation of the apparatus inaccomplishing this is believed to be as explained hereinafter.

With application of 110 volts across the terminals 45 and 46, there is avoltage applied to the primary windings 21 and 3| reinforced by thevoltage in the auxiliary starting secondary winding 25 which isconnected thereto in autotransformer relationship, so that the totalvoltage which will be induced between terminals 5| and 56 will appearacross the lamp 4|. Through proper design of the windings, this voltagewill be of the order of 800 volts, with practically no drop occurringacross the capacitor since no current flows prior to ignition. TheVoltage is more than suflicient to ignite lamp 4| and with ignition,current will begin to flow through the lamp 4|, causing the voltage todrop to approximately 250 volts, which is slightly higher than operatingvoltage for the T-12 watt instantstart fluorescent lamps. The flow ofcurrent causes a quadrature component of voltage to appear in thewinding 25 such that the resultant voltage is actually opposite indirection to that giving rise to the voltage 25'. Hence, with flow ofcurrent, the resulting voltage becomes 25".

Referring now to Figs. 1 and 2 it will become apparent that the winding25 is physically separated from the primary winding 21 by a magneticshunt 25 whose effect is to constitute the winding 25 a high leakagereactance very loosely coupied with the primary winding 2'1. Thelooseness of the coupling is even more enhanced by the fact that thesecond primary winding 3| is remote from the auxiliary winding 25. Thisarrangement aids in the voltage reversal which is so desirable, in amanner to be pointed out, and the splitting of the primary winding hasan addihigh flow of current tional purpose, which will also be setforth. With the voltage of winding725 reversed, same is additive to theleading secondary winding 28. The winding 25 has a great many turnscompared with the turns of the windings 2! and 3! constituting theprimary and hence a large voltage is induced therein, so that thecomponent in phase with that of leading secondary winding 28 issuflicient to cause ignition of the lamp 44. The circuit now becomes aseries circuit, since the leakage reactance of the winding 25 is veryhigh compared with the reactance of the branch including the leadingsecondary winding 23 and condenser 55. The efiect is that the currentflows from juncture 55 through lamp 4!, condenser 55, juncture 56,winding 28, and lamp M to the juncture 52. The condenser 55 is chosen sothat the resulting power factor is leading to balance the lagging powerfactor of the second branch whose operation will now be explained. Priorto going into such explanation, it is desired to point out that theoperation of the leading branch of the circuit is substantiallyidentical to that described in connection with the above referred toapplication of Feinberg Serial No. 135,669.

Considering now the inductive, Or lagging aranch of the apparatus, notethat the lagging secondary winding 29 is separated from the secondprimary winding 3! by a considerable mag netic shunt to aid in thedecoupling effect there between and likewise is separated from theleading secondary winding 23 for the sam reason. This is to preventinterference between the respective fluxes. However, if the circuitwhich includes the primary windings 2? and 3! and the lagging secondarywinding 29 is traced, it will be noted that the induced voltages are allin the same direction. Because of this, upon the closing of the circuitto the line terminals 45 and the voltages appearing in the primarywindings 2? and Si and in the lagging secondary winding 29 are additive.The total voltage which is of the order of 800 volts appears across lamp52 and is sufficient to ignite the same.

Before ignition of lamp 32, there is no current flowing in the circuitwhich includes the lamp 63. Consequently the condenser 58 has very lowimpedance, and practically no voltage drop appears across lamp 43. Afterignition, the voltage across the lamp 42 drops to substantiallyoperating value and current flows in the leads 69 and BI, but by-passingthe lamp 43 through the branch containing the resistor 51 and thecapacitor 58. As for the entire circuit from juncture 52 to the juncture5!, through the lagging secondary winding 29, the impedance is loweredbecause of the counter-balancing effect of the high leakage reactance ofthe lagging secondary winding 29 with the leading reactance of thecondenser 58. There is thus a relatively therein, and the voltageresulting across the capacitor 58 is well over 600 volts and quitesuflicient to ignite the lamp 43. The presence of the resistor addsslightly to this voltage, but is not considered essential. Actually theresistor 51 has a low ohmage, and its purpose is to dampen oscillatingcurrents in the shunting branch of the lamp 43 in the well-known manner.

Once current has commenced flowing through the lamp 43, its voltagedrops approximately to the operating value and 'due to the highimpedance of the condenser 53 with the relatively low voltage dropacross it, the circuit including the two lamps 42 and 43 becomes aseries cir- 8. cuit in which current and hence operating voltages of thelamps are limited by the inductive reactance of the lagging secondarywinding 29. The net power factor of this series circuit is thus lagging,and when considered in connection with the leading power factor of thecircuit including the lamps M and 44, the net effect upon the line isthat the apparatus draws current at a power factor approaching unity.

It should be appreciated that the two circuits, i. e., the leading andthe lagging are energized simultaneously, so that first the lamps s: and42 are ignited, and thereafter the lamps 43 and 44 are ignited.

The physical position of the auxiliary starting secondary winding may bevaried from that shown. It may for example, be positioned at theopposite end of the transformer 28, that is, it may be arranged as shownin Fig. 4 where the first primary winding 21 is at the extreme left endof the transformer 26 and the windings 28, 29, and follow in that orderseparated as shown by the magnetic shunts 38 and 32. The secondarywinding 25 is now at the extreme right end and the magnetic shunt 26separates it from the second primary winding 3i, serving the samepurpose as the magnetic shunt 25 of Fig. 1. In all other respects theapparatus is the same as described above, and operates in the identicalmanner.

Analyzing the overall operation of our apparatus it will become apparentthat the lead circuit is ignited by the aid of an inductive reactance,namely the auxiliary starting secondary winding 25, while the lagcircuit is ignited by the aid of a capacitive reactanee, namely thecapacitor 58. We have found that the use of lagging impedance to start aleading circuit and a leading impedance to start a lagging circuitenables the eventual desired result for quick starting and long life ofthe fluorescent lamps to be achieved in a highly economical manner. Suchlong life is made possible only when all of the lamps carrysubstantially the same rated current during operation. The reason suchan arrangement will provide the desired results is that after ignitionof the first lamp of any twolamp series circuit it becomes necessary todevelop a high voltage across the first lamp without causing too great acirculating current through the auxiliary starting impedance. Ourarrangement provides the necessary igniting voltage for the second lampWithin the requirements set forth. Thus, an additional capacitor in thelead 6! between the lamp 43 and the coil 29 of a size sufiicient to makethe circuit leading would prevent the development of sufficient voltageacross the lamp 4% to ignite the lamp while enabling suflicient currentto pass to originally ignite lamp 42. In such case the voltage suppliedby the primary windings and the lagging coil would have to be muchhigher to assure ignition of lamp 63. As a result coil 29 would. have tobe larger and the currents between lamps 42 and 43 would tend to beunbalanced.

The same analysis can be made to show that it is inadvisable to use aninductive impedance as the auxiliary starting element for a serieslagging circuit.

As well-known in the art, it is highly advantageous to achieve asclosely as possible, perfectly sinusoidal wave shape in this type ofapparatus. The maximum of lighting efficiency and minimum losses areamong the most important of these advantages.

In our apparatus,-

'novelmeans for accomplishing this have" been devised. The principalcircuit in which this must be done is the leading circui The commonmethod of doing this has been to utilize a separate choke in the leadingcircuit. As noted, this is eliminated by our invention. The method shownand described in Berger Patent No. 2,461,957 is not feasible in ourapparatus because of the high magnetizing current developed in ourprimary.

The problem of non-sinusoidal wave form is important in the case ofapparatus providing leading lamp currents because of the with whichsaturation of iron cores is reached under those circumstances. Thus, itmust be expected that saturation will occur in transformers used in thetype of apparatus described unless something is done to prevent it. Inorder est to co ridor the manner in which we have prov ed the occurrence of saturation of transformer core, attention is invited to thevector diagram of Fig. 5. This shows the common condition giving rise tosaturation. In Fig. 6 another vector diagram shows the manner in whichour construction alleviates this disadvantageous phenomenon.

Considering first Fig. 5, there is shown a vector diagram of thevoltages (and hence the fluxes) occurring in an iron core transformerwhich is serving a leading fluorescent lamp circuit having a capacitortherein. The transformer was d signed for a secondary open circuitvoltage of AD with its corresponding flux density. Presume a transformerhaving a primary and a secondary with a lamp connected in series withthe secondary and having a condenser in the circuit to make the circuitdraw leading current. Let AB oi Fig. represent the voltage across thefluorescent lamp during steady state operation (disregarding theinductance of the lamp). Let BF represent the voltage drop across thecondenser and E0 the drop across the secondar tending to balance out thecapacitive drop, making a net voltage of as the effective net capacitivedrop. Now, if AC is the total open circuit voltage (considering thetransformer as an auto-transformer), it must consist of the primaryvoltage DC and the secondary voltage AD. Now the voltages AB and DC mustvectorially add to give AC, and since DC is fixed as the open primaryvoltage, we may consider that all of the reactive impedance occurs inthe secondary, and therefore, we may transfer the vector FC to the pointD to determine the actual secondary voltage. The transferred reactivevoltage is represented by the vector ED. The resultant voltage is thenAE, the voltage of the secondary which obviously is substantially largerthan the secondary open circuit voltage for which the transformer wasdesigned, namely AD. The voltage AE therefore represents a flux densitygreatly in excess of optimum causing the iron core to be saturated withresulting distortion of the current feeding the lamp.

The above explanation is to demonstrate why it is most likely thatsaturation will occur in the leading circuits oi apparatus described. Wehave provided means for preventing such saturation. In our apparatus itwill be noted that we have positioned a portion of the primaryphysically remote from the remainder of the primary winding. Thus,referring to Figs. 1 and 2, note that the primary consists of the firstprimary winding 21 and the second primary winding 31 which is separatedtherefrom by the windings 28 and 28, and the magnetic shunts 30 and 32.Actually, in the apparatus described, the shunts were and 10respectively. A considerable leakage of flux will occur across thelagging secondary winding 29 and through the shunts. The leadingsecondary winding 23 is thus effectively separated from the secondprimary winding 35 as is the first primary winding 2?.

When the leading circuit is in operation, with the lamps 4! and 45ignited, the resultant voltage appearing across the leading secondarywinding 22 and giving rise to the flux or voltage represented by thearrow 28 would normally tend to saturate the core of the transformer 29.This voltage is the equivalent of the voltage AE represented in Fig. 5.However, the magnetic iiux which tends to produce the voltage in thewinding 23 is to a considerable extent bypassed by the leakage acrossthe lagging secondary winding 29 and through the magnetic shunts 3c and32 whose reluctance to the passage of flux is considerably less thanthat of the saturated core adjacent the leading secondary winding 28.The open circuit voltage of the winding 28 (corresponding to the vectorAD in Fig. 5) will thus drop, causing a corresponding drop in theresultant voltage and a partial elimination of the saturation condition.

The remaining correction of the flux shape is provided by the properarrangement of the lagging secondary winding 25 Winch, it will be notedin Fig. 3, produces a flux represented by the arrow 25 in buckingrelationship relative to the primary winnings 2i and 3E. In order bestto explain this corrective action, attention is invited to the vectordiagram oi Fig. 6.

Consider a simple auto-transformer circuit having a lamp in series withthe secondary. The voltage drop through the lamp is A's and the reactivevoltage drop is now BC which is due to the iealrage reactance or thesecondary. 'rhe total open circuit voltage is AC made up of tne primaryopen circuit voltage WC and the secondary open circuit voltage AD. As inthe case or log. 5, the voltage of the primary DC being fixed, the totalreactance drop must occur across the secondary and can be shown bytransferring the voltage B0 to the polnt D to give LL86 to the shntedvector The resultant voltage across the secondary is now the sum or theV011)- ages and which vectorially gives the voltage As will be noted,this may be considerably less than the voltage A'D' and or substantialphase dnierence. rne nux caused by the voltage Ahl' Will. beproportional thereto and or the same phase.

Now note that the lagging secondary winding 29 will produce tne type ornux mentioned in connection with the vector diagram 01' Fig. 6, andproportional to the voltage described as This winding is positionedbetween the leading secondary winding 28 and the second primary winding31, being physically separated lrom them by the shunts 6E and 52respectively. mince the flux through the winding 29 is less than normaland snirted in phase, the iiux between the second primary ti and theleading secondary winding 28 tends to be reduced, and the resultantvoltage across the leading secondary winding will be reduced in additionto the factor caused by splitting the primary. The resulting wave shapeor current approaches sinusoidal quite satisfactorily.

The same effect, namely the counteraction of the saturation flux causedin the leading secondary winding 28 can be achieved in the transformer20, by winding a portion of the leading secondary winding 28 directlyupon the lagging secondary winding in reverse relationship in order toprovide the benefits of the bucking flux and reducing the total fluxdensity and hence the resultant voltage in the leading secondary. Suchan arrangement is shown and described in Feinberg co-pending applicationSerial No. 97,381 hereinabove referred to. This expedient may be used toadvantage under circumstances where the position of the laggingsecondary winding 29 is insufiicient to provide counter-flux, or otherdesign considerations prevent the use of the construction illustrated inFig. 1.

The split primary feature of our invention is described and claimed inco-pending application Serial No. 154,094, filed April 5, 1950, entitledApparatus for Operating Gaseous Discharge Devices.

With respect to maintenance of fluorescent lighting fixtures, onefeature of the apparatus described above is advantageous. In the eventthat lamp ii should become deactivated, both lamps ii and d will becomeextinguished. In the event lamp l i becomes de-activated, then lamp E!will glow because there will be a small amount of current passed by thewinding 15. Thus, it is a simple matter to determine which lamp needsreplacing. If both lamps ii and 6d are extinguished, the faulty lamp isprobably ii, or possibly both lamps, while if lamp 4' 5 is extinguishedand lamp ii glows, the fault lies in lamp 46;

Similarly, with respect to the lagging circuit, in the event lamp 42 isfaulty both lamps will extinguish, while if lamp 43 is tie-activatedlamp 422 will still glow. Thus one knows which lamp of this circuit mustbe replaced.

In the event that the fluorescent lamps need not be connected directlyto the power line modifications in our apparatus will decrease the costthereof. In the event it is still desired that the removal of the lampopen the power circuit, special sockets may be used which operate aswill be described hereinafter. Such apparatus is less expensive becauseof the advantage that certain parts of the windings may be combined.

Thus, in Fig. 7 we have shown apparatus for igniting and subsequentlyoperating four fluorescent lamps. The arrangement of the windings isshown in Fig. 8. The transformer 79 is constructed substantially thesame as the transformer 29, although it may be considerably smaller. Thewindows carry the windings 8%, 8i, 82, 83, 8t and 85 as will bedescribed. Three magnetic shunts 85, S7, and 88 with their associatednon-magnetic gaps 89, SIB, and SI separate the windings in a manner tobe described. The primary winding 88 is connected across the lineterminals 92 and 93 and is in autotransformer relationship with thesecondary winding 8! with which itis closely'coupled. The primary andsecondary windings 8t and 8| are wound one on top of another in the samewindow. The winding 82 is the auxiliary starting winding having afunction similar to the winding 25 hereinabove referred to, but now withits voltage in reverse relationship to windings 8G, 8! and 83 and saidwinding 82 is in series with the winding 8I, but is positioned in thefirst window of the transformer I9 as will be noted in Fig. 8. Theleading secondary windin 83 is in series with the winding 82, and isphysically positioned in the third window, separated from the primaryand secondary windings 80 and 8| by the narrow shunt 81'. The laggingsecondary windin 8 is positioned at the extreme right end of thetransformer 80 i2 and has the bucking leading secondary winding woundthereon and closely coupled therewith.

The leading series circuit consists of the lamp 9 connected in serieswith the leading secondary windings 83 and 85, and the lamp connected inseries with a condenser 96 across the auxiliary starting secondarywinding 82. The lagging series circuit consists of the lamp 9? connectedin series with the lagging secondary winding 84, and the lamp 98 shuntedby the condenser 99 and resistor IEO in series with the Winding 84. Theleft hand ends of the lamps 94 and 91 as viewed in Fig. '7 are connectedto the terminal 92 of the line, while the left hand ends of both lamps95 and 98 are connected to the juncture IQI.

The leading and lagging secondary windings 83 and 84 can be made verymuch smaller than in the case of the apparatus described in Figs. 1, 2,and 3. For the same open circuit voltage, one turn can be removed fromeach of these windings and placed upon the secondary winding 8|, in amanner described in detail in co-pending appli cation of Feinberg SerialNo. 97,381. Likewise, each turn removed from the leading secondarywinding 83 enables a turn to be removed from the bucking leadingsecondary winding 3'5. The function of the winding 85 is to correct waveshape in the manner explained in said Feinberg application Serial No.97,381. Note that the two lamps s5 and Q8 do not terminate at laceswhere their removal can open the line.

Referring now to Fig. 9, there is illustrated a socket which can be usedin connection with the embodiments illustrated in Figs. '7 and 8. Thelamp 12c has a single male contact terminal I2! adapted to be associatedwith socket I22. Socket E22 has a central movable member 123 looselymounted in a transverse wall I25 and adapted to slide right and left.The right end has a head I25 and slides in a cavity I253 adapted toreceive the terminal I2I. The cavity I26 has opposed contacts I21 andI28 connected with leads I29 and 239 respectively. Obviously insertingthe terminal IZI into cavity I26 will connect leads I29 and I38 whilethe lamp I29 will be likewise connected to the juncture. Such a juncturecould be that represented at iSI in Fig. '7, for example. The member I23is biased to the right by spring I32 which is disposed about the body ofmember I23. The left end of the member 23 is provideo. with a conicalmetal contact ti I33 which is slidable in cavity I3 l. J uxtaposedcontacts I35 and I36 are connected with the respective leads I37 and:35. When the member I23 is moved to the left it will cause electricalcontact to be made between leads I37 and I38 thereby closing the circuitof such leads. This point could be at I39 in Fig. 7, for example.

It will be seen that by the use, with the fluorescent lam fixtures, oisockets I22 such as shown in Fig. 9, a cheaper construction of ballastis possible. Note that the circuits represented by leads I3II38 andi2t-I3z'i are in no way electrically connected since the body of memberI23 is formed of any suitable insulating material.

t will be apparent that a general feature that the embodiments of ourinvention have in common is their use of two apparently separate seriescircuits, each having two lamps therein arranged for series starting andseries operation, but all operating oil a single transformer. The twocircuits of each embodiment are opposite in their overall reactivecharacter, that is to say, one is inductive and the other capacitive sothat not only is the stroboscopic effect of the lamps materiallyreduced, but as well, the line power factor may approach unity. Sincethe lamps of each circuit light one after the other, one lamp of eachcircuit may be eliminated if desired. The necessary circuit constantadjustments for proper operation can readily be made. The resultingcircuit will thus operate two lamps or three. Thus, in the circuit shownin Figs. 1 to 3 inclusive, the lamp 4| may be eliminated, so that theapparatus will ignite and operate three lamps. The condenser 55 in thiscase would be connected with the juncture 5|. Illustration of thismodification is not made since it is simple and readily understood.

In the same apparatus, as an alternative, or in addition, the lamp 43and its shunt could be eliminated leaving the remainder of the circuit,in case it is desired to have only one lamp on the lagging side. Thiswould provide either a three-lamp ballast or a two-lamp ballast. As atwo-lamp ballast, the construction would be expensive, but same isdescribed herein to illustrate that the two circuits are effectivelyindependent of one another. The modifications to the lagging circuit arebelieved obvious enough not to require illustration.

We have constructed and successfully operated apparatus embodying ourinvention for igniting and operating groups of fluorescent lamps of theinstant-start type from 118 volt A. C. power lines. Such lamps were ofthe type known as T42 75 watt, 96 inch instant-start lamps, having anignition voltage of 625, operating voltage of 195 volts and an operatingcurrent of 430 milliamperes. The constructional details (referring toFigs. 1 to 3) of the apparatus were as follows;

Overall length of the core inches. Width of core 2! 3 inches. Width ofwinding leg 22 linch. Height of stack 1% inches. Width of windows andwindings;

Secondary winding 2'5 inch. Primary winding 2'! 1% inches. Secondarywinding 28 2 inches. Secondary winding 29 2 inches. Primary winding 3|1% inches. Widths of shunts:

26 inch. 30 inch. 32 %inch. Widths of gaps;

33 .010" 34 .040" 35 .040" Condensers:

55 .25 microfarads rated at 900 volts A. C. 58 .2 microfarad rated at900 volts A. C. Resistor 51 500 to 1500 ohms. Winding turns:

25 3200 turns of No.

34 wire. 21 200 turns of No.

18 wire. 28 2115 turns of No.

26 wire. 29 2070 turns of No.

26 wire. 3| 200 turns of No.

18 wire.

The electrical characteristics of the apparatus were as follows:

Volts Open circuit voltage across the lamp 4l 800 Open circuit voltageacross the lamp 42 700 Open circuit voltage across the lamp 43 770 Opencircuit voltage across the lamp 44 800 The voltages across lamps 43 and44 were measured with lamps 4i and 42 in place and vice versa.

During operation the voltage across all lamps was approximately 200volts, and the current flowing in each circuit was approximately 430milliamperes. lhe line voltage was 118 volts and the current drawn fromthe line was 3.5 amperes.

The modifications shown in Fig. 4 was also constructed using the samegeneral physical dimensions and characteristics. The variations from theembodiments of Figs. 1 to 3 were minor.

The invention has been described in connection with certain theoriesadvanced which may or may not supply the exact reasons for the operationthereof. It is intended not to be limited by such theories, or by anabsence of language describing other theories, but it is intended thatthe structures producing the desired results and engendering thedescribed advantages, be covered in their broadest scopes. Examples ofall possible variations of the structure have not been specificallydetailed as to dimensions and characteristics since it is believed thatfrom the specification herein, and other specifications herein referredto, one skilled in the ballast art could easily and readily constructsame.

We claim:

1. A system comprising a transformer of elongate iron core formation andunitary construction providing a single magnetic circuit for ignitingand operating gaseous discharge devices from an A. C. power line ofvoltage less than the igniting voltage of any device, including windingmeans providing a source of voltage mounted on said transformer core forserving secondary windings of said transformer, an A. C. power lineleads connecting said source winding means to the said line, said sourcewinding means having end terminals; two sub-circuits, one sub-circuitbeing a leading current circuit and having a first secondary windingwith one side connected to one of said terminals, a second secondarywinding connected to the second side of the first secondary winding, afirst gaseous discharge device electrically connected from the secondside of the second secondary winding to one of the terminals of thesource winding means, a condenser, a second gaseous discharge deviceconnected in series with the condenser and together therewithelectrically connected from the second side of the first secondarywinding to the terminal of the source winding means opposite that towhich the first gaseous discharge device is connected, the firstsecondary winding being disposed on one end of said core and havingmagnetic shunt means between itself and the remainder of the transformerwhereby same is loosely coupled to the source winding means to develop ahigh leakage reactance in said first secondary winding, and the secondsecondary winding being relatively closely coupled to the source windingmeans, the first and second secondary windings being connected in opencircuit voltage opposition one relative the other, and a secondsub-circuit being a lagging current circuit and having a third secondarywinding connected in auto-transformer relation with the source windingmeans and having. a third gaseous discharge device in series therewithand connected across said source winding means, the third secondarywinding being disposed on the core and there being magnetic shunt meansphysically spacing said third secondary winding from the other windingsand the source winding means.

2. A system as described in claim 1 in which the second gaseousdischarge device of said first sub-circuit is connected together withsaid series condenser only across said first secondary winding, and inwhich the first gaseous discharge device is connected across thecombined windings of the first and second secondaries and the sourcewinding means.

3. A system as described in claim 1 in which the second gaseousdischarge device of the first sub-circuit is connected together withsaid series condenser across the combined first secondary winding andsource winding means, while the first gaseous discharge device isconnected across the first and second secondaries combined.

4. A system as described in claim 1 in which the source winding meanscomprises two series arranged windings with the said leads connectedacross one of the windings to constitute same a primary winding and theother a source secondary winding in auto-transformer relation, thesource secondary winding being closely coupled to the primary winding.

5. A system as described in claim 1 in which there is a fourth secondarywinding connected in series with and voltage additive relation to saidsecond secondary winding but physically positioned on said core closelycoupled with the said third secondary winding and in voltage oppositionthereto, the said fourth secondary winding being electrically connectedin said circuit as though it were a part of said second secondarywinding.

6. A system as described in claim 4 in which there is a fourth secondarywinding connected in series with and voltage additive relation to saidsecond secondary winding but physically positioned on said core closelycoupled with the said third secondary winding and in voltage oppositionthereto, the said fourth secondary winding being electrically connectedin said circuit as though it were a part of said second secondarywinding.

7. A system as described in claim 1 in which said source winding meanshas said leads connected to said terminals, said second gaseousdischarge device having one end thereof electrically connected to saidopposite terminal, and

said third gaseous discharge device has one end thereof electricallyconnected to a terminal, and in which said leads are provided with pairsof spaced apart contacts, there being as many pairs as dischargedevices, and each device has a bridging conductor at the end thereofwhich is electrically connected to a terminal as aforesaid, saidconductors engaging and bridging the contacts of the respective pairs tocomplete the connection between the power line and source winding meansthrough said leads, only when all of said devices are connected in theirrespective subcircuits.

8. A system as described in claim 1 in which the second sub-circuitincludes a fourth gaseous discharge device also in series with saidthird secondary winding and having means shunting said fourth gaseousdischarge device during starting of the third gaseous discharge device.

9. A system as described in claim 7 in which the second sub-circuitincludes a fourth gaseous discharge device also in series with saidthird secondary winding and having a shunting impedance thereacross, andwith an end of said fourth gaseous discharge device also electricallyconnected with a terminal, provided with a bridging conductor andengaged and bridged between a pair of spaced apart contacts of saidleads.

10. A system as described in claim 1 and including a socket for one ofsaid gaseous discharge devices, said device having a projectingconductor end and said socket having two pairs of spaced apart contacts,the first pair being in one of said leads, and the second pair being ina part of one of said sub-circuits not connected to a lead, the pairsbeing insulated from one another, a movable insulating member having abridging contact for the first pair but said member being biased tonon-bridging position, the movable member having an end disposed betweenthe contacts of the second pair, said end adapted to be engaged by saidconductor while said conductor is moved into engagement with said secondpair whereby to move same against said bias.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 1,689,485 Hendry Oct. 30, 1928 1,950,396 Boucher Mar. 13, 19342,056,661 Foulke Oct. 6, 1936 2,295,757 Russell Sept. 15, 1942 2,305,487Naster Dec. 15, 1942 2,352,073 Boucher et a1 June 20, 1944 2,355,360Boucher et a1 Aug. 8, 1944 2,427,225 Mueller Sept. 9, 1947 2,429,162Keiser Oct. 14, 1947 2,429,415 Lemmers Oct. 21, 1947 2,464,971 FloodMar. 22, 1949 2,502,084 Foerste Mar. 28, 1950 2,504,549 Lemmers et a1 -1Apr. 18, 1950 2,510,209 Bridges 1 June 6, 1950 2,515,109 Berger July 11,1950 2,545,164 Naster Mar. 13, 1951 2,552,111 Peterson May 8, 1951

